Chlorination system with corrosion minimizing components

ABSTRACT

A pumping apparatus for pumping a liquid from a source to a target including a motor and pump driven by the motor. Sacrificial zinc components are utilized to minimize corrosion due to chlorine vapors. Measures to ensure that liquid is pumped in only one direction include the use of a full wave rectifier and/or a spacer incorporated with a swivel platform to limits the range of the angle between the motor shaft and the pump piston. To minimize the risk of rupturing the pump, the pump piston includes a relieved portion in fluid communication with a transverse bore of the pump housing when the piston is axially inserted within the pump housing in its full forward position. To prevent overheating and damage to the pump components, the pumping apparatus makes use of a positive temperature coefficient (PTC) resistor interposed between the motor and a current source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. Ser. No.11/414,703, filed Apr. 28, 2006, now U.S. Pat. No. 7,785,084, which is acontinuation-in-part of U.S. Ser. No. 11/226,733, filed Sep. 14, 2005,now U.S. Pat. No. 7,387,502, which claims the benefit of U.S.Provisional Application No. 60/610,471, filed on Sep. 16, 2004 and U.S.Provisional Application No. 60/612,621, filed on Sep. 23, 2004.

FIELD OF THE INVENTION

The present invention relates generally to liquid pumping systems,wherein one liquid is pumped or fed into the stream of another liquid.More particularly, the present invention relates to a method andapparatus that minimizes gases in the liquid pumping system.

BACKGROUND OF THE INVENTION

There are situations in which it is necessary to inject or feed oneliquid into the stream of another liquid. Some liquid pumping systemsrequire an occasional injection of liquid while others need a morecontinuous feed of the liquid. Still others might require a combinationof the two. For purposes of this disclosure, it is understood that theterm “feed” will include inject.

One such common application is in the field of water treatment whereincertain chemicals, such as chlorinating solutions, fluorinationchemicals and other liquids, are fed into the water stream at a pointprior to its delivery for end use by consumers. It is important tomaintain certain percentage levels of these added liquids in order toassure adequate functionality without exceeding predeterminedconcentrations which could be objectionable or even harmful to theconsumer.

A variety of apparatus is available in the industry to perform thischemical feed task. Such apparatus typically takes the form of a pump,wherein pump speed and chemical feed rate is controlled by well knownelectronic means which employs chemical concentration detection meansand provides voltage or current signal output for use by the pump drivesystem to adjust its feed rate. This system operates in a closed loopfashion to maintain a relatively stable concentration of the desiredchemical in the water stream.

Certain chemicals, particularly sodium hypochlorite (NaOCl) solutionused for chlorination of the water system, exhibit the troublesomecharacteristic of constant gas generation. Specifically, the liquidNaOCl spontaneously outgases in such a way that bubbles form in conduitpiping, fittings and any other cavities in the feed circuit. Positivedisplacement pumps attempting to draw this liquid from storage tanks andfeed it into the water stream can become gas-bound when encounteringsuch gas bubbles. Once gas-bound, the pump will simply work against a“springy” bubble, which will alternately compress and expand to entirelydevour the pump's displacement stroke volume. At this point, feeding ofliquid chemical into the water stream ceases and the pump will uselesslyrun without effect.

This problem is aggravated by the often encountered requirement to feedthe liquid chemical directly into a pressurized water stream. Here, evena modest sized gas bubble will give rise to a gas bound condition as thepump unsuccessfully attempts to compress the gas sufficiently to forceit out of the pump chamber against the water stream back pressure. Theproblem is sufficiently severe that certain water treatment facilitiesundertake the extra step of diluting the sodium hypochlorite solution inthe liquid chemical supply tank in order to reduce gas bubble formation.It can be reliably stated that the most aggravating problem known in thewater chlorination and disinfection industry is the off-gas generated bythe sodium hypochlorite NaOCl solution.

Another related problem is associated with priming. Once a chemicalvessel is emptied, the feed apparatus will draw in air and entirely fillthe intake circuit (including tubing, fittings, internal chambers andsuch) with this air. The chemical concentration detection apparatus willthen signal or alarm for intervention by a technician. Chemical feedrestoration now requires that a full liquid chemical vessel besubstituted for the empty vessel followed by a troublesome and timeconsuming sequence of valve openings/closings by a skilled technician tobleed offending air out of the circuit in order to prime the pump. Onlyafter the technician confirms by observation that the feed pump isactually feeding liquid into the water stream can the task be consideredcompleted. This problem of manual bleeding is common to any liquidchemical application and is in addition to and apart from theout-gassing characteristics of NaOCl solutions.

Numerous attempts have been made to solve the problems described herein.For example, it is known in the field to incorporate a solenoid operatedpurge valve in a liquid pump, which is manually or automaticallyoperated to divert the pressure output port of the feed pump away fromthe pressurized water stream and back to the liquid chemical supplytank. Once liquid has filled the pump circuit, the valve is shifted backso as to direct the chemical liquid into the pressurized water stream.However, the drawbacks of such prior art solutions include complexelectronics, additional valves, manual intervention or urgent attentionon the part of technicians.

Another problem associated with liquid NaOCl pumping systems is thecorrosive effect that chlorine vapors have on the various metalcomponents of the system. Specifically, metal screws, clamps, and evenstainless steel components are vulnerable to corrosion by exposure tothese chlorine vapors.

Still another design consideration with such pumping systems is thenecessity that the system only pump in one direction. For example, inthe field of water treatment, wherein a chlorinating solution is fedinto a water stream, it would be very detrimental if the pumping systemwere to malfunction and pump in the reverse direction whereby water fromthe water stream is pumped into a liquid NaOCl supply. Since most motorsused in such pumping applications are typically direct current (DC)motors, such malfunction could occur, for example, if the polarity ofthe current flowing to the motor were somehow reversed. Reversed pumpingcan also occur if the pumps and motor couplings are not properlyoriented with respect to the motor upon installation.

The pumps themselves must also be carefully designed to prevent anyleakage. Proper operation of these pumps is largely dependent on theprecise angular and axial orientation of the pump piston with respect tothe pump's inlet and outlet ports. Any misalignment between the two canresult in a pressure build-up within the pump causing the end cap of thepump housing to rupture.

Another difficulty encountered in certain pumping applications of thistype has been associated with loss of supply liquid. This can occur ifthe pumping unit is installed in a remote location with little or noroutine maintenance, combined with no monitoring of supply vessel liquidlevel. In such situations, loss of supply liquid to the pumping unitwill result in termination of “hypo” injection into the water stream.This loss of supply liquid will be detected by monitoring equipment,which normally controls the pumping injection rate by speeding up thepump motor or slowing it down accordingly when free supply liquidpercentages fall or rise.

The loss of supply liquid will, if not corrected, lead the detectionequipment to attempt to raise the supply liquid levels by directing themotor of the pumping unit to increase its speed. This speed willincrease all the way to maximum, where it will remain until a technicianintervenes. Such intervention may not occur for hours or days. Meanwhilethe pump will be running at high speed with no liquid to cool orlubricate its moving parts. It has been found under such circumstancesthat the pump components will heat up from friction effects to the pointwhere drag gradually increases and the pump eventually seizes. This cansometimes cause the drive motor to burn out if the drive electronics isnot adequately fused or the pump elements can become fused together suchthat full dismantling is required in order to free them.

Accordingly, it is desirable to provide a simply designed system,wherein gas bubbles are dispatched automatically while replacement of anempty liquid chemical supply tank and commissioning of a new full tankis simply done by switching input tubing from the empty to the fulltank. It would be further desirable to provide an apparatus requiring nopriming and does not require the pump to be turned off when changingliquid supplies. It would also be desirable for such an apparatus toinclude pumps that are substantially leak-free, rupture-free and lessprone to chemical precipitate build-up with resultant mechanicalfailure. It would still be further desirable to provide a liquid NaOClpumping system that is less vulnerable to the corrosive effects thatchlorine vapors have on the various metal components of the system andthat is safe-guarded for pumping in only one direction. It would also bedesirable to provide a liquid pumping system that will not be damaged inthe event of a loss of supply liquid.

SUMMARY OF THE INVENTION

The present invention is a pumping apparatus for pumping a liquid from asource to a target including a motor, a first pump driven by the motor,a second pump driven by the motor and a separator in fluid communicationwith the first and second pump for separating a liquid received from asource into a gaseous component and a liquid component. The separatorfurther diverts the gaseous component to the first pump and the liquidcomponent to the second pump, wherein the first pump pumps the gaseouscomponent back to the source and the second pump pumps the liquidcomponent to a target.

In a preferred embodiment, the separator is a T-fitting having adownward oriented arm for separating the liquid component under theinfluence of gravity and permitting horizontal flow of the gaseouscomponent. The apparatus further preferably includes a substantiallyvertically oriented tube connecting the downward arm of the T-fitting tothe pump. Also, the motor, the first pump and the second pump aresubstantially horizontally arranged.

The pumping apparatus of the present invention is preferably containedin a portable and mountable case having an inlet mounted thereon forfluidly connecting the separator to the liquid source, a gas outletmounted thereon for fluidly connecting an output port of the first pumpto the liquid source and a liquid outlet mounted on the case for fluidlyconnecting an output port of the second pump to the target. The casefurther preferably includes a hinged cover for permitting access to themotor, pumps and separator contained in the case and a drain outlet fordraining any fluid leakage from the interior of the case. The hingedcover may be suspended from the case in a substantially horizontalposition by a lanyard.

The pumping apparatus can be provided with a wash-water subsystem forcleaning the first and second pumps. The wash-water subsystem preferablyincludes tubing connected to the first and second pumps for deliveringwash-water to the pumps and a flow restrictor for regulating the flow ofthe wash-water to the pumps.

The present invention further involves a method for pumping a liquidfrom a source to a target. The method generally includes the steps ofseparating the liquid into a gaseous component and a liquid component,diverting the gaseous component to a first pump, diverting the liquidcomponent to a second pump, pumping the gaseous component back to theliquid source with the first pump and pumping the liquid component tothe target with the second pump.

Thus, the present invention calls for the use of a separate pump whosefunction is to draw whatever is in the intake line up to a point abovethe intake for the primary feed pump. At this point there is a T-fittingwith a large diameter pipe connection leading downwards to the intakeport of the main feed pump. The output line of the first pump isconnected to tubing which leads back to the liquid chemical supply tank.There is little or no restriction to the flow of liquid through thefirst pump so it experiences no difficulty drawing gas, liquid or acombination thereof out of the chemical supply tank and returning itback again to this same tank.

As liquid or gas passes over the down facing port of the T-fitting onits way to the input of the first pump, liquid falls down under theinfluence of gravity to the intake port of the primary feed pump (secondpump). This intake port, in turn, is angled upwards so that it becomesflooded with liquid. A suitably designed pump is then able to self clearsmall amounts of gas so long as its intake port is flooded with liquid.

In a preferred embodiment, at least one of the pumps of the presentinvention includes a pump housing and a pump piston. The pump housingdefines a central longitudinal bore, a transverse bore communicatingwith the central bore for conveying a liquid through the pump housingand a liquid reservoir communicating with the central bore and thetransverse bore for retaining an amount of the liquid conveyed throughthe transverse bore. The pump piston is axially and rotatably slidablewithin the central longitudinal bore for pumping the liquid through thetransverse bore.

In this embodiment, the pump housing further preferably includes aninlet port and an outlet port, and the transverse bore includes an inletportion extending between the inlet port and the central bore and anoutlet portion extending between the central bore and the outlet port. Apressure relief slot is preferably formed in the central bore betweenthe inlet portion of the transverse bore and the liquid reservoir tofacilitate liquid flow therebetween. The central bore further preferablyterminates at an opening formed in the housing. The piston extends outfrom the opening and the pressure relief slot extends from the inletportion of the transverse bore to the housing opening.

A lip seal assembly is preferably disposed at the housing opening forsealing the piston. The lip seal assembly includes two annular lip sealshaving lip portions in sliding contact with the piston. The lip portionsof the lip seals are bent outwardly away from the housing opening tofacilitate scraping of the piston. In this regard, the piston furtherpreferably includes an outer surface having a vapor-depositedpolytetrafluoroethylene (PTFE) coating.

The present invention further involves a method for preventing theformation of precipitates in a liquid chlorine solution pump. The methodincludes the steps of moving a piston within a bore of the pump to drawliquid chlorine solution into the pump, moving the piston within thebore to force liquid chlorine solution out of the pump and retaining anamount of the liquid chlorine solution in a liquid reservoir formed inthe pump. The liquid reservoir is in fluid communication with the pumpbore and the amount of the liquid chlorine solution retained in thereservoir is sufficient to prevent crystallization of the chlorinesolution in the pump during an idle period of the pump. The volume ofliquid retained by the reservoir is preferably at least approximately0.7 cc. Retaining an amount of liquid chlorine solution in the liquidreservoir essentially decreases the surface to volume ratio of theliquid chlorine solution, thereby reducing evaporation and consequentialformation of crystals within the pump.

As described above, one embodiment of the present invention provides fora wash-water subsystem configured to continuously flush the pumpsinternal structures. This is done for two reasons:

-   -   Reduce crystallization caused by evaporation of sodium        hypochlorite.    -   Establish a water barrier between the sodium hypochlorite and        the lip seals, thereby assuring that any leakage past said lip        seals is merely water and not sodium hypochlorite solution.

An unanticipated consequence of this arrangement is that, in certainsituations, dissolved metallic salts in the wash water (notably thecopper salts) can react with the sodium hypochlorite solution to forminsoluble precipitates which can build up on the internal structures ofthe pump and ultimately lead to seizure of the moving parts. Suchdissolved metallic salts can be eliminated through the use of purifiedwater but the cost and additional complications associated with thisarrangement has led to the improved non-wash water embodiment describedherein.

In a preferred embodiment, the step of drawing liquid chlorine solutioninto the pump involves the step of creating a negative pressure in aninlet of the pump and the step of forcing liquid chlorine solution outof the pump involves the step of creating a positive pressure in anoutlet of the pump. The inlet and the outlet are in fluid communicationwith the liquid reservoir, whereby the negative and positive pressuresinduce a flow of liquid chlorine solution between the liquid reservoirand the inlet and the outlet via a pressure relief slot formed in thepump bore. This negative pressure is communicated directly to the lipseal area such that, in the absence of a positive pressure, sodiumhypochlorite solution is encouraged to stay inside the pump instead ofbeing expelled past the sealing face of the lip seal.

The present invention further preferably utilizes sacrificial zinccomponents to minimize corrosion due to chlorine vapors. Specifically,in a preferred embodiment, the chlorination system of the presentinvention includes a source of chlorine solution, a mounting platecomprising zinc, a motor mounted to the mounting plate and a first pumpmounted to the mounting plate and driven by the motor for pumping thechorine solution from the source into a supply of water. In a preferredembodiment, the mounting plate is a steel plate coated with zinc.

As described above, a second pump mounted to the zinc coated mountingplate is preferably utilized in conjunction with a separator in fluidcommunication with the source of chlorine solution and the first andsecond pumps for separating chlorine solution received from the sourceinto a gaseous component and a liquid component. The separator furtherdiverts the gaseous component to the second pump and the liquidcomponent to the first pump, wherein the second pump pumps the gaseouscomponent back to the chlorine solution source and the first pump pumpsthe liquid component into the supply of water.

In this embodiment, the motor and the pumps are preferably mounted tothe zinc coated mounting plate with zinc die-cast fasteners, (althoughstainless steel fasteners can also be used). In addition, the motorpreferably includes a rotatable motor shaft, a zinc coated mountingplate in contact with the motor shaft via a steel bearing and aspherical steel coupling coupled between said motor shaft and said firstpump.

The present invention further preferably takes measures to ensure thatliquid is pumped in only one direction. In one embodiment, electricalmeasures are taken, wherein the pumping apparatus generally includes adirect current motor and a full wave rectifier. The motor has arotatable motor shaft, a positive input terminal and a negative inputterminal and the full wave rectifier is interposed between the motor anda current source supplying electrical current to the motor. The fullwave rectifier has a positive output terminal and a negative outputterminal, wherein the positive output terminal is electrically connectedto the positive input terminal of the motor and the negative outputterminal is electrically connected to the negative input terminal of themotor, whereby a desired polarity of current flows to the motor toensure that the motor shaft rotates in only one direction, therebycausing the first pump coupled to the motor shaft to pump liquid in onlyone direction from a source to a target.

In an alternative embodiment for ensuring pumping in only one direction,the pumping apparatus generally includes a support frame, a motormounted on the support frame, a swivel platform pivotably mounted on thesupport frame, a drive assembly connected with the support frame and theswivel platform and a pump mounted on the swivel platform. The driveassembly pivots the swivel platform with respect to the support frameand includes a drive rod and a spacer. The drive rod is coupled to theswivel platform and the support frame and the spacer is engageablebetween the support frame and the swivel platform to prevent furtherpivoting of the swivel platform with respect to the support frame. Thepump includes a rotatable and axially translatable piston coupled to themotor shaft of the motor, wherein pivoting of the swivel platform by thedrive means changes an angle defined between a longitudinal axis of themotor shaft and a longitudinal axis of the pump piston and the spacer ofthe drive assembly limits the range of said angle.

In this embodiment, the drive rod is preferably in the form of athreaded rod rotatably retained on opposite sides of the support frameand threadably engaged with the swivel platform. The spacer ispreferably in the form of a tubular sleeve member surrounding a portionof the threaded rod. Also, the support frame preferably includes aninner pocket having a width for receiving the swivel platform, whereinthe inner pocket defines a range of pivoting of the swivel platform. Inthis case, the threaded rod and the spacer are disposed within the innerpocket, and the spacer has a length substantially equal to half thewidth of the inner pocket.

To minimize the risk of rupturing the liquid pump of the presentinvention preferably includes a pump housing defining a centrallongitudinal bore and a transverse bore communicating with the centralbore and a rotatable pump piston axially slidable within the centrallongitudinal bore between a fully retracted position and a full forwardposition for pumping the liquid through the transverse bore. The pumppiston includes a relieved portion in fluid communication with thetransverse bore of the pump housing when the piston is axially insertedwithin the pump housing in its full forward position.

In this embodiment, the relieved portion of the pump piston ispreferably defined by a planar surface, wherein the planar surfacedefines a zero reference plane when the piston is axially insertedwithin the pump housing in its full forward position. This zeroreference plane is disposed at an acute angle with respect to the centeraxis of the transverse bore. This acute angle is preferably about 5degrees. The pump housing further preferably includes a piston linerdefining the central longitudinal bore and the transverse bore and apump casing surrounding the piston liner. The pump casing has areference surface aligned with the zero reference plane of the pumppiston, wherein the piston liner is rotated with respect to the pumpcasing about a center axis of the central longitudinal bore.

To prevent overheating and damage to the pump components, the pumpingapparatus of the present invention preferably includes a motor, acurrent source supplying electrical current to the motor and a positivetemperature coefficient (PTC) resistor interposed between the motor andthe current source. The positive temperature coefficient (PTC) resistorhas a current trip value, wherein current from the current sourceexceeding the current trip value causes a resistance of the positivetemperature coefficient (PTC) resistor to rise to a value such thatcurrent to the motor decreases. A visual indicator is also preferablyprovided for indicating when the current from the current source hasexceeded the current trip value of the positive temperature coefficient(PTC) resistor.

As a result of the present invention, an apparatus is provided whichutilizes a novel means for dealing with the presence of gas in theliquid chemical intake plumbing. Also, the design of the presentinvention further provides the ability to self prime against apressurized system, even in the event of total gas entrainment into theintake liquid circuit. Thus, the present invention is particularlysuitable for use as part of a chlorination system for delivering achlorine solution into a water supply.

The preferred embodiments of the apparatus and method of the presentinvention, as well as other objects, features and advantages of thisinvention, will be apparent from the following detailed description,which is to be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of the pumpingapparatus formed in accordance with the present invention.

FIG. 2 is a perspective view of the pumping apparatus shown in FIG. 1contained in a compact mountable case.

FIG. 3 is a cross-sectional view of an alternative embodiment of thepumping apparatus formed in accordance with the present invention.

FIG. 4 is a cross-sectional view of the preferred embodiment of the pumpaccording to the present invention.

FIG. 5 is a cross-sectional view of the pump shown in FIG. 4 taken alongline 5-5.

FIG. 5 a is a cross-sectional view of an alternative embodiment of thepump shown in FIG. 4 taken along line 5-5.

FIG. 6 is an enlarged cross-sectional view of the pump seals shown inFIG. 4.

FIG. 7 is a cross-sectional view of the pump piston coupling accordingto the present invention.

FIGS. 8 a and 8 b are electrical circuit diagrams for the electricalsystem for preventing reverse pumping according to the presentinvention.

FIG. 9 is a diagrammatic cross-sectional view of the pump/motorcoupling.

FIG. 10 a is a plan view of the pump and pump/motor coupling angularlyoriented to pump fluid in the correct direction.

FIG. 10 b is a plan view of the pump and pump/motor coupling, whereinthe pump has been angularly pivoted resulting in fluid flow in the wrongdirection.

FIG. 11 a is a top perspective view of the pump support assembly of thepresent invention, with the pump removed, and the swivel platformpivoted in a first position.

FIG. 11 b is a top perspective view of the pump support assembly of FIG.11 a with the swivel platform pivoted in a second position.

FIG. 11 c is an isolated top perspective view of the swivel platformguide block.

FIG. 12 is a bottom perspective view of the swivel platform shown inFIGS. 11 a and 11 b.

FIG. 13 is a cross-sectional view of the pump shown in FIG. 4 takenalong line 13-13.

FIG. 14 is an electrical circuit diagram for the electrical system forpreventing damage to the pump motor according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate the preferred embodiment of the presentinvention. The present invention is a pumping apparatus 10, whichgenerally includes a first pump 12 and a second pump 14 coaxiallymounted to and driven by a motor 16. When the motor 16 is energized itdrives both pumps 12 and 14 simultaneously.

Pumps 12 and 14 are preferably positive displacement pumps oriented in ahorizontal arrangement wherein the axes of the pumps are generallyhorizontal with respect to the motor 16, as shown in FIG. 1. A desirablepump for use in the present invention as the first pump 12 is the “ROPump” supplied by Fluid Metering, Inc., Syosset, N.Y. (www.fmipump.com).A desirable pump for use in the present invention as the second pump 14is the “Q-1CTC Pump” also supplied by Fluid Metering, Inc.

A desirable DC motor for use in the present invention is a motor similarto Groschopp Part No. PM6015 supplied by Groschopp, Inc., 420 15^(th)Street NE, Sioux Center, Iowa, with modifications, including a shorteroverall length and stainless steel shafts. Other modifications to themotor in accordance with the present invention are described in detailfurther below.

While the first pump 12 is being driven by the motor 16, it draws aliquid into its intake port 18 via an intake conduit 20. At its oppositeend, the intake conduit 20 is connected to an inlet 22, which in turn isadapted to be connected to a liquid source, such as a cistern 24containing a chemical to be injected or fed into a main fluid stream 26,as shown in FIG. 3. The inlet 22 is preferably a quick-connect typefitting adapted to be fluidly connected to a hose, a pipe or other typeof conduit 28 leading to the liquid source 24.

Interposed along the path of the intake conduit 20, between the intakeport 18 of the pump 12 and the inlet 22, is a separator 30 forseparating the liquid supplied from the liquid source 24 into a gaseouscomponent and a liquid component. The separator 30 is preferably ajunction, such as a T-fitting, oriented along the path of the intakeconduit 20 to facilitate horizontal flow through the fitting and havingone arm 32 oriented vertically downward. In this manner, as a gas/liquidmix passes through the T-fitting 30, the liquid component of the mixturefalls downward through the vertical arm 32 of the fitting under theinfluence of gravity.

Any gaseous component of the liquid fed through the inlet 22 flowshorizontally through the T-fitting 30 and is drawn into the intake port18 of the first pump 12. This gaseous component is then discharged outof an output port 34 of the first pump 12 into a gas return tube 36,which terminates at a gas outlet 38 of the apparatus 10. The gas outlet38 is also preferably a quick-connect type fitting adapted to beconnected to a return line 40 running back to the liquid source 24, asshown in FIG. 3.

The vertical arm 32 of the T-fitting 30 is connected to a verticallyoriented, large diameter liquid feed tube 42, which, at its oppositeend, is connected to an intake port 44 of the second pump 14. Thisliquid feed tube 42 is preferably of large enough bore to avoid trappingbubbles under a liquid column. Experimentation has suggested that tubingwith an internal diameter of about ⅜″ works nicely in this regard.

The vertical orientation of the liquid feed tube 42 further ensures thatthe degassed liquid which has fallen down from the vertical arm 32 ofthe T-fitting 30 displaces any gas at the intake port 44 of the secondpump 14. As a result, the second pump 14 is now self-priming.

The second pump 14 discharges the degassed liquid out of an output port46 into a liquid discharge tube 48, which is connected to a liquidoutlet 50. The liquid outlet 50 is again preferably a quick-connect typefitting, which is adapted to be connected to an inlet 52 of the mainfluid stream 26 via a liquid feed line 54, as shown in FIG. 3. Thesecond pump 14 thus delivers the degassed liquid to the main fluidstream 26 against the pressure head of the main supply.

The system 10, according to one embodiment of the present invention,further includes a wash-water subsystem 56 for lubricating and cleaningout the pumps 12 and 14. Specifically, each pump head 58 of the pumps 12and 14 preferably include a feature called an “Isolation Gland” or “WashGland” wherein the pump head includes a pair of extra ports 60 which areconnected to wash-water lines 62. The wash-water lines 62 fluidlyconnect a wash-water supply port 64 to a wash-water waste port 66,wherein the pump heads 58 may be connected in series along thewash-water line path, as shown in FIGS. 1 and 2, or they may beconnected in parallel, as shown in FIG. 3.

The wash-water subsystem 56 further preferably includes a flowrestrictor 68 for restricting the flow of the incoming wash-water intothe wash-water supply port 64 before the water enters the pump heads 58.A suitable flow restrictor for use in the present invention is a 150mL/min restrictor.

The wash-water subsystem 56 provides the function of maintaining cleanpumps as described above and also provides a sort of lubrication to helpthe pump start up after extended periods of non-operation. The purposeof the flow restrictor 68 in the present invention is to regulate theamount of wash-water which is introduced into the wash glands of the twopump heads 58. Municipal water sources generally provide water atelevated pressure (upwards of 100 psig) and connections are made tolarge gate valves at convenient plumbing locations. Thus, regulation ofwater flow from these large valves, which normally are used to controlrates of tens of liters per minute, through the device becomesimportant. The flow restrictor 68 eliminates any need on the part of theinstaller or maintenance technicians to adjust their water supply flowrate or pressure.

The pump system 10, according to the present invention, is preferablycontained in a compact mountable box or case 70, as shown in FIG. 2. Inparticular, the components of the system 10 are conveniently containedwithin a case 70 having a hinged cover 72 with the inlet 22, the gasoutlet 38, the liquid outlet 50, the wash-water inlet 64 and thewash-water outlet 66 extending from the exterior of the case. Thus, thecase 70 can be mounted to a wall, for example, wherein the system 10 canbe connected to on-site fluid lines via the various fluid connections22, 38, 50, 64 and 66 which extend outside of the case.

In this regard, the cover 72 is preferably hinged to the case 70 to openin a downward direction when the case is mounted to the wall. The cover72 further preferably includes at least one lanyard 74 for suspendingthe cover in a horizontal orientation with respect to the case. In thismanner, the cover 72 provides a shelf for placing tools or other itemsduring servicing or repair of the system. Preferably, the cover 72defines an interior compartment 76 for holding such tools or spareparts.

The case 70 further provides convenient structure for mounting anelectrical terminal 78 for providing electrical power to the motor 16from an electrical source via electrical wiring (not shown) fed throughan external electrical port 80 of the case. The electrical terminal 78and port 80 are preferably mounted to an interior surface of the casegenerally above the pumping components so that any leakage in the systemwill not come into contact with the electrical connections of theterminal.

The case 70 further preferably includes a drain outlet 82 provided in abottom surface of the case to drain any leakage in the system out of thecase. The drain outlet 82 is preferably in the form of a check-valve ora ball-valve, which permits only one-way fluid flow out of the case 70.As a result, exterior contaminants are prevented from entering the case.

As mentioned above, the pumps 12 and 14 and the motor 16 are orientedhorizontally. The purpose for this orientation is to prevent anypossible damage to the electric motor 16 from liquid leakage which mightissue from a pump 12 or 14. Specifically, when the pumps 12 and 14 areoriented horizontally with respect to the motor 16, any leakage from apump will simply fall to the bottom of the case 70 and will be drainedout of the case via the drain outlet 82.

An added advantage in orienting the assembly horizontally is improvedperformance with respect to liquid/gas separation. The horizontalassembly arrangement as shown in FIGS. 1 and 2 allows for a relativelystraight vertical liquid feed tube 42, which facilitates bubbles risingto the top thereby readily separating the entrained gas bubbles. Thefull range of flow angles for the pumps 12 and 14 (typically rangingfrom 7.5°-to-22°) are accommodated by this arrangement.

Nevertheless, it is totally conceivable to orient the pumps 12 and 14,with respect to the motor 16 in a vertical arrangement, as shown in thealternative embodiment of FIG. 3. This may be necessary, for example,due to the on-site limitations in installing the system. In thisembodiment, the first pump 12 is positioned above the motor 16 and thesecond pump 14 is positioned below the motor. Operation of the system10, however, is identical to that described above.

FIG. 4 shows a preferred embodiment of a pump 100 for use in the presentinvention. The pump 100 generally includes a pump housing 101 and apiston 118. The pump housing 101 preferably includes a plastic pumpcasing 102 having an inlet port 104 and an outlet port 106. The pumpcasing 102 is preferably made from a rigid polyvinyl chloride (PVC) anddefines a cylindrical chamber 108 having an open end 110. Received inthe cylindrical chamber 108 is a ceramic piston liner 112 having acentral longitudinal bore 114 and a transverse bore 116 communicatingwith the longitudinal bore. The transverse bore 116 includes an inletportion 116 a fluidly communicating with the inlet port 104 of the pumpcasing 102 and an outlet portion 116 b fluidly communicating with theoutlet port 106 of the pump casing so that a liquid, such as a chlorinesolution, can be pumped from the inlet port, through the liner, to theoutlet port in a manner as will be described below.

The pump 100 further includes a ceramic piston 118 axially and rotatablyslidable within the central bore 114 of the piston liner 112. One end ofthe piston 118 extends out of the open end 110 of the pump casing 102and includes a coupling 120 for engagement with a motor. At its oppositeend, the piston 118 is formed with a relieved portion 122 disposedadjacent the transverse bore 116 of the pump liner 112. As will bedescribed below, the relieved portion 122 is designed to direct fluidinto and out of the pump 100.

A lip seal assembly 124 is provided at the open end 110 of the pumpcasing 102 to seal the piston 118 and the pump chamber 108. The lip sealassembly 124 is retained at the open end 110 of the pump casing 102 by agland nut 126 having a central opening 128 to receive the piston 118.The gland nut 126 is preferably attached to the pump casing 102 with athreaded connection 130 provided therebetween.

In operation, a motor (not shown in FIG. 4) drives the piston 118 toaxially translate and rotate within the central bore 114 of the pistonliner 112. In order to draw liquid into the transverse bore 116 from theinlet port 104, the piston 118 is rotated as required to align therelieved portion 122 with the inlet port. The piston 118 is then drawnback as required to take in the desired volume of liquid into thecentral bore 114 of the pump liner 112. Withdrawal of the piston 118produces a negative pressure within the inlet portion 116 a of thetransverse bore 116, which draws in liquid from the inlet port 104. Thepiston 118 is then rotated to align the relieved portion 122 with theoutlet port 106 of the pump casing 102. Finally, the piston 118 isdriven forward the required distance to force liquid into the outletport 106 via the outlet portion 116 b of the transverse bore 116 toproduce the desired discharge flow.

When pumping liquids with the pump shown in FIG. 4, some of the liquidwill invariably seep into the space between the piston 118 and thepiston liner 112. As mentioned above, one problem with pumping certainliquids, particularly NaOCl solutions, is the tendency for the liquidtrapped between the piston 118 and the liner 112 to evaporate andcrystallize during pump idle time. Such crystallization can build up onthe piston 118 and eventually cause it to seize within the pump liner112. As mentioned previously, precipitates resulting from reaction ofthe sodium hypochlorite solution and metallic salts, which may bepresent in wash water, can also contribute to this seizing problem.Elimination of the wash water will preclude any precipitates which arereaction products, but that leaves the problem of crystallizationunsolved.

A solution to this crystallization problem is to form the pump liner 112with a liquid reservoir 132 in communication with the central bore 114of the liner. The liquid reservoir 132 allows a sufficient volume ofliquid to be maintained around the pump piston 118 so as to preventcrystallization of the liquid. Specifically, by trapping a sufficientvolume of liquid within the liquid reservoir 132, the surface to volumeratio of the liquid surrounding the piston 118 is decreased, therebydecreasing the tendency for the liquid to evaporate and crystallize. Ithas been found that at least approximately 0.7 cc of liquid volume issufficient to prevent crystallization of the liquid.

The liquid reservoir 132 can take the form of a transverse bore 134formed in the liner 112 and having a width greater than the diameter ofthe liner central bore 114, as shown in FIG. 5. Alternatively, theliquid reservoir 132 can take the form of an annular counter-bore 136formed in the liner 112 surrounding the liner central bore 114, as shownin FIG. 5 a. Also, a counter bore 137 may be provided in the liner 112surrounding the central bore 114 at the open end 110 of the liner inaddition to the liquid reservoir 132. The counter bore 137 provides anadditional reservoir for storing lubricating liquid.

It can thus be seen that the liquid reservoir 132 eliminates the needfor a wash-water system 56, as described above. Instead, lubrication andcleaning of the pumps, which had been provided by the water of thewash-water system, is now achieved by the pumping liquid. Eliminatingthe wash-water system results in only one liquid being present withinthe pump, thereby eliminating the chance of adverse liquid mixingreactions (e.g., copper and rust contamination).

To increase the fluid flow surrounding the piston 118 and therebyfurther decrease the chance for this liquid to evaporate, the liner 112is further preferably formed with a pressure relief slot 138 (alsotermed a “scavenger slot”). The pressure relief slot 138 communicateswith and extends longitudinally along the central bore 114 of the liner112 from the open end 110 of the liner to the inlet portion 116 a of thetransverse bore 116. The pressure relief slot 138 thus formedfacilitates fluid flow back to the inlet portion 116 a of the transversebore 116 due to the negative pressure created at the inlet portion bymovement of the piston 118. In other words, the negative pressurecreated at the inlet portion 116 a of the transverse bore 116 tends todraw the liquid surrounding the piston 118 back to the inlet portion viathe pressure relief slot 138. Also, since the outlet portion 116 b ofthe transverse bore continuously sees a positive pressure, even duringpump idle times, any migration of trapped liquid toward the negativepressure inlet portion 116 a will be replaced with fresh liquid therebyfurther inhibiting crystallization.

An additional benefit of the pressure relief slot 138 is a reduction inleakage from the open end 110 of the piston casing 102. As describedabove, the pressure relief slot 138 draws the liquid away from the openend 110 of the pump casing 102 toward the transverse bore 116. Thus, thenatural tendency of the fluid flow will not be toward the open end 110of the casing 102. This enables the lip seal assembly 124 to be arrangedin an advantageous manner. Specifically, rather than having two lipseals arranged “back-to-back,” wherein the lips of the seal are bent inopposite directions, the lip seal assembly of the present invention caninclude two ceramic loaded polytetrafluoroethylene (PTFE) lip seals 140sandwiched together such that their bent lips 142 both face outwardlyaway from the interior chamber 108 of the piston casing 102, as shown inFIG. 6. A white Teflon washer 144 may also be provided between the lipseals 140 and the gland nut 126 to help secure the lip seals against theopen end 110 of the pump casing 102. The washer 144 can also beinterposed between the lip seals 140, wherein the bent lips 142 of eachlip seal are separated from each other a distance equal to the thicknessof the washer.

By having both lip portions 142 face away from the interior of the pumpcasing, any debris from erosion of the lip seal 140 will tend to travelaway from the interior of the pump rather than travel into the pump. Thebenefit again is to reduce the chance of material entering the pump andcausing the piston to seize.

Also, having both lip portions 142 of the seal facing outwardlyincreases the scraping ability of the lip seal to remove any debris orresidue from the outside of the piston 118 before entering the pump. Inthis regard, it is preferred to coat the outside of the ceramic piston118 with a vapor-deposited polytetrafluoroethylene (PTFE) coating, asdescribed in commonly owned U.S. Publication Nos. 2004-0241023-A1 and2005-0276705-A1.

As mentioned above, another problem associated with liquid NaOCl pumpingsystems is the corrosive effect that chlorine vapors have on the variousmetal components of the system. To offset this problem, the presentinvention utilizes sacrificial zinc components in electrical contactwith the various other metal components of the pumping system, such asmetal screws, clamps and piston couplings, which are vulnerable tocorrosion by exposure to these chlorine vapors.

In particular, the entire pumping apparatus 10 is preferably mounted toa hot or cold-dipped zinc back plate 150, which in turn is attached tothe plastic case 70 via zinc die-cast screws or stainless steel screws152, as shown in FIGS. 1 and 2. Where possible, all metal components ofthe pumping apparatus 10 are mechanically and electrically connected tothe zinc coated back plate 150. For example, the pump mounting bases154, the electrical terminal 78 and the various hose clamps (not shown)for securing the apparatus 10 are all attached to the zinc back plate150 via zinc die-cast screws 152. Also, zinc washers 156 are preferablyprovided under the terminal screws 158 of the electrical terminal 78.

By placing all steel and aluminum components in contact with a zinccomponent in this manner, it has been found that the steel and aluminumcomponents are protected from chlorine vapor corrosion by the mechanismof cathodic protection. Cathodic corrosion protection is well understoodand relies on the use of a sacrificial active metal, which acts as ananode in electrolytic coupling to a less active metal. Such anodeprotectors are often used in water tanks and attached to boat hulls inorder to protect the more noble metals from corrosion.

In situations where steel and aluminum components are not easily put incontact with the zinc back plate 150, the present invention utilizesother sacrificial zinc components. Specifically, the motor 16 of thepumping apparatus 10 according to the present invention is preferablymounted to a zinc coated mounting plate 160, which is in contact withthe steel motor shaft 162 via a steel bearing 164. Also, the motor 16 ispreferably provided with zinc alloy housing end caps 166 to providefurther cathodic corrosion protection to the steel components of themotor.

As shown in FIG. 7, the steel pin 120 a and aluminum coupling 120 b forconnecting the ceramic piston 118 of the pump 100 to the motor 16 can becathodically protected from corrosion by replacing the nylon bearing,typically used in such motor/pump couplings 168, with a steel bearingrace 170. The steel bearing race 170 rotatably receives a sphericalsteel ball 171 connected to the pump piston 118 and is retained withinan aluminum pump coupling housing 172, which in turn is fixed on the endof the motor shaft 162. As discussed above, the motor shaft 162 is incontact with the zinc motor mounting plate 160 and/or the zinc housingend caps 166 of the motor 16. Thus, an electrical path is providedbetween the steel pump coupling 120 and the zinc motor mounting plate160 and/or the zinc housing end caps 166, whereby these zinc componentsare sacrificed to protect the steel pump coupling 120 from corrosion.

It should further be explained that, although the zinc parts aresacrificed in order to protect the steel and aluminum parts, this is anextremely slow process, because the chlorine vapor corrosion is far morelimited in its capacity to consume the zinc than would be the case forparts immersed in solutions of salt or NaOCl. This means that the zinccoatings and zinc parts show very slight loss of mass in thisapplication while performing their role of cathodic corrosionprotection.

As also discussed above, still another design consideration with suchpumping systems is the necessity that the system only pump in onedirection. Unfortunately, detrimental reverse pumping can occur if thepolarity of the current flowing to the preferred DC motor 16 weresomehow reversed. To ensure pumping in only one direction, regardless ofthe polarity of the current, the present invention preferably makes useof a full wave rectifier 174 in a unique manner to convert input directcurrent of either polarity to direct current of the desired polarity.

As is well known in the art, full wave rectifiers are conventionallyused to convert alternating current (AC) to direct current (DC).However, as shown in FIGS. 8 a, 8 b and 14, the present inventionutilizes a full wave rectifier 174 connected between the direct currentsource 176 and the motor 16 to convert input direct current of eitherpolarity to direct current of the desired polarity. In particular, thepositive output terminal of the full wave rectifier 174 is electricallyconnected to the positive input terminal of the motor 16 and thenegative output terminal of the rectifier is electrically connected tothe negative input terminal of the motor 16. The full wave rectifier 174restricts the flow of positive current to its positive output terminalregardless of the polarity of the current received at its inputterminals. Thus, the desired polarity of the current flowing to themotor 16 can be guaranteed and, as a result, the motor shaft will rotatein only one desired direction. A suitable full wave rectifier 174 foruse with the present invention is Digi-Key P/N KBL01-E4/51GI-ND,supplied by Digi-Key Corporation.

Another way reversed pumping can occur is if the pumps and motorcouplings are not properly oriented with respect to the rotational axisof the motor shaft. To ensure proper orientation of the pumps withrespect to the rotational axis of the motor shaft, the present inventionutilizes a mechanical stop means that prevents the pump from beingmisaligned with the motor shaft axis.

As described above, and with reference to FIGS. 4, 7 and 9, the motor 16drives the piston 118 of the pump 100 to axially translate and rotatewithin the central bore 114 of the piston liner 112 between the inletport 104 and the outlet port 106. The piston 118 is rotated as requiredto align the relieved portion 122 with the inlet port 104 and is thendrawn back as required to take in the desired volume of liquid into thecentral bore 114 of the pump liner 112. The piston 118 is then rotatedto align the relieved portion 122 with the outlet port 106 of the pumpcasing 102. Finally, the piston 118 is driven forward the requireddistance to force liquid into the outlet port 106 to produce the desireddischarge flow.

This combined axial and rotational motion of the pump piston 118 isachieved by orienting the rotational axis of the pump piston 118 at anangle α0 with respect to the rotational axis of the motor shaft 162 andusing a spherical ball and socket coupling 168 to couple the motor shaftto the pump piston, as is diagrammatically shown in FIG. 9. As can beunderstood with regard to positive displacement pumps of this nature,the greater the angular displacement α between the pump piston 118 andthe motor shaft 162, the greater the axial displacement of the piston118 in the pump which causes a higher rate of fluid flow. As therotational axis of the piston 118 is brought closer in alignment to therotational axis of the motor shaft 162, the displacement of the pumpingpiston becomes smaller within the pump, resulting in a lower volume offluid flow. When the pump piston 118 and the motor shaft 162 aresubstantially coaxially aligned with each other, (i.e., when α=0), thepiston will have no stroke nor will it reciprocate upon rotation. Thus,no pumping action takes place in this position.

As is shown in FIGS. 10 a and 10 b, the angular orientation of the pumppiston 118 with respect to the motor 16 also determines the direction ofpumping for the pump 100. Thus, with the pump 100 angularly orientedwith respect to the motor 16, as shown in FIG. 10 a, the piston 118 willbe oriented and operate to correctly pump liquid out of the outlet port106 while the opposite port serves as the inlet port 104. When the pump100 is pivoted in a counter-clockwise direction from the axially alignedmiddle position, as shown in FIG. 10 b, the direction of the fluid flowwill reverse resulting in the port 104 becoming the outlet port and port106 becoming the inlet port. Once again the magnitude of the angulardisplacement of the pump piston 118 from the middle position willdetermine the amplitude of piston stroke, and, consequently, the rate offluid flow.

Referring additionally to FIGS. 11 a, 11 b and 12, to accurately set theangle α between the rotational axis of the pump piston 118 and therotational axis of the motor shaft 162, the pump 100 and motor couplingassembly 168 are preferably mounted on a pump support assembly 180. Thepump support assembly 180 generally includes a support frame 182, aswivel platform 184 pivotable within the support frame and a driveassembly 186 for pivoting the swivel platform within the support frame.The pump 100 is mounted on the swivel platform 184 of the supportassembly 180, which permits swivel movement of the pump 100 angularlywith respect to the support frame 182 both clockwise andcounterclockwise.

The swivel platform 184 pivots about a bearing means in the form of twoperpendicular posts 188, which act cooperatively with an indicator edge190 on the platform 184 as it bears against a cam surface 192 formed inthe support frame 182 so that dual pivot axes are established to controldeflection of the platform 184. One of the bearing posts 188 is used foreach direction of angular deflection of the piston and cylinder withrespect to the pump drive axis. Thus, the cam surface 192 is provided topermit freedom to only one bearing post to float at a time, and toprovide directional restraints to permit such float in only onedirection for each bearing post. As a result of this unique arrangement,when both axes are restrained simultaneously, there is no angulardeflection nor piston reciprocation, and thus, no fluid being pumped. Apump support assembly of this type is shown and described in commonlyowned U.S. Pat. No. 4,941,809, the specification of which isincorporated herein by reference in its entirety for all purposes.

The support assembly 180 further includes a drive assembly 186 toaccurately pivot the swivel platform 184 within the support frame 182.The drive assembly 186 includes a fine threaded rod 194, rotatablyretained on opposite sides of the support frame 182, a knob 196 forrotating the rod and an internally threaded guide block 198 threadablyengaged with the rod. The guide block 198 is attached to the bottom ofthe swivel platform 184 and is driven by the threaded rod 194 to pivotthe platform within the support frame 182. Specifically, as the rod 194rotates, the threaded engagement between the rod and the guide block 198will cause the guide block to traverse along the length of the rod. Thisin turn will cause the swivel platform 184, which is attached to theguide block 198, to pivot within the support frame 182. Referringadditionally to FIG. 11 c, to facilitate such movement, the guide block198 can be pivotably attached to the swivel platform 184 throughengagement of a slot 198 a by a pin extending from the bottom of theswivel platform 184, or the guide block can be provided with aninternally threaded swivel bearing to receive the rod 194.

To prevent the swivel platform 184 from pivoting too far into a positionwhere reverse pumping will occur, as shown in FIG. 10 b, the driveassembly 186 of the present invention further includes a spacer 200. Thespacer 200 is a tubular member having an inner longitudinal bore sizedto receive the threaded rod 194. The length of the spacer 200 isselected to match roughly half the width of the inner pocket 202 of thesupport frame 182. As will be described in further detail below, thiswill restrict pivoting of the swivel platform 184 within only one halfof the support frame 182.

In use, rotation of the threaded rod 194 within the guide block 198 andthe spacer 200 will cause the swivel platform 184 to pivot about an arcwithin the lower half of the support frame 182, as shown in FIG. 11 a.Continued rotation of the threaded rod 194 in one direction will casethe swivel platform 184 to reach the mid-point 204 of the support frame182, as shown in FIG. 11 b, wherein the pump piston 118 will be axiallyaligned with the shaft 162 of the motor 16. At this point, one end ofthe spacer 200 makes contact with the guide block 198, while the otherend of the spacer makes contact with an inner wall 206 of the supportframe 182, thereby stopping any further movement of the swivel platform184. Thus, the length of the spacer 200 should be precisely selected topermit the swivel platform 184 to pivot to a position where the pumppiston 118 and the motor shaft 162 are axially aligned, but to restrictany further movement of the swivel platform. As a result, the pump 100is prevented from ever being pivoted into a position where reversepumping can occur, as shown in FIG. 10 b.

Another feature of the present invention involves the measures taken toprevent leakage and ensure proper operation of the pumps. Specificallyreferring to FIG. 13, (which is a cross-sectional view of the pump 100,shown in FIG. 4, taken along the line 13-13), the pump 100 of thepresent invention is designed to prevent hydraulic lock by ensuring thatany liquid held in the relieved portion 122 of the piston 118 is nottrapped when the piston 118 moves to its forward most extended positionwithin the pump's axial bore 114. In other words, the design of the pump100 of the present invention continues to allow fluid to escape throughthe pump outlet 106 as the piston 118 moves to the end or bottom of itsstroke.

In conventional pumps of this type, the inlet and outlet portions of thepump liner are oriented generally parallel with the flat surface of thepiston relieved portion when the piston moves to the end of this stroke.However, any misalignment between the two can result in fluid beingtrapped in the relieved portion as the piston moves to the end of itsstroke. Thus, a pressure build-up within the pump causing can occurcausing the end cap of the pump housing to rupture.

The present invention solves this problem by ensuring that the fluid canescape the relieved portion of the piston as the piston moves to the endof its stroke. This is achieved by angularly orienting at least theoutlet portion 116 b of the transverse bore 116 of the piston liner 112with respect to the “zero reference plane” 210 of the pump piston 118,wherein the “zero reference plane” of the pump piston 118 is defined bythe plane formed by the flat surface 122 a of the relieved portion 122of the piston 118 when the piston is at its forward most position,(i.e., the end of its stroke) within the pump axial bore 114.

The simplest way to angularly orient the transverse outlet portion 116 bis to rotate the piston liner 112 within the pump casing 102 by an angleθ. Typically, the pump casing 102 has a reference mounting surface formounting the pump to a pump support assembly, as described above. Themotor 16 is also mounted to the pump support assembly and is orientedwith respect to the reference mounting surface of the pump so that themotor shaft and the pump piston 118 will be properly oriented withrespect to the inlet 104 and the outlet 106 of the pump 100. Therefore,by simply rotating the pump liner 112 by an angle β within the pumpcasing 102, the outlet portion 116 a of the transverse bore will beproperly positioned with respect to the zero reference plane 210 of thepump piston 118. It has been found that the angle 13 of rotation ispreferably about 5°.

It is conceivable that other methods can be used to position the outletportion 116 b of the pump liner 112 to the desired position. Forexample, the entire pump 100 can be oriented at a 5° angle with respectto the motor 16. Alternatively, the outlet portion 116 b itself can beformed in the pump liner 112 at an angle or offset from the inletportion 116 a.

In any event, the objective is to ensure that any liquid trapped in therelieved portion 122 of the piston 118 when the piston is at its mostextended position will have an egress 212 through which the liquid canescape without being further compressed. Thus, during its output stroke,the piston moves to the bottom of its travel, while the outlet portremains open. This will prevent a pressure build-up in the axial bore,which could result in a pump failure.

Another feature of the present invention involves an electricalarrangement provided for preventing damage to the pump motor 16, andother pump components, should there be depletion in the amount of supplyliquid. As shown in FIG. 14, a method for dealing with this problem hasbeen conceived, wherein a self resetting fuse-type of device 220 isadded in series with the power wires of the motor 16. The device isknown as a positive temperature coefficient (PTC) resistor, or varistor,and has the electrical symbol 220 shown in FIG. 14.

The electrical characteristic of this device 220 is most importantly thecurrent at which it switches to its high resistance state. Below thiscurrent, the PTC 220 will remain at a low resistance, allowing currentto flow without attenuation to the motor 16 so that the pump is drivenat speeds up to its full rated rotational velocity. Should the motordriving current exceed the PTC's trip value, its resistance will quicklyrise to a very high value such that driving current to the motor 16drops to a very low value.

In practice, typical driving circuitry to the motor 16 willautomatically compensate for increased motor load by increasing voltagein order to achieve desired motor RPM. This voltage increase then leadsto an increase in current flow. The facility of the motor driver circuitto increase current in the presence of increased pump load is utilizedin the contemplated circuit modification to protect the pump. Suchincrease in load will be encountered when the driven pumps are beginningto seize because of running dry at high speed.

Measurements were made of current needed to drive the motor at variousspeeds with the highest pumping conditions of pressure and flow. Thesemeasurements revealed under non-seizing conditions the data shown below:

100 psi Wet Amps RPM 0.39 950 0.38 1060 0.39 1180 0.38 1290 0.38 13900.38 1500 0.37 1610

Based upon these data, a Bel Fuse Inc. part number OZRC0025FF1E wasselected and installed in series with the motor wires of the systemaccording to the present invention. This device has a “trip” current of0.50 amp, which allows the pump to run unimpeded so long as frictionloads caused by prolonged dry running do not call for excess drivecurrent. Upon artificial application of external drag on the pump drivespindle, the unit was observed to stop without damage to any of thesystem components.

Once tripped, it is advantageous for the PTC 220 to remain in its highresistance protective state with very small current flow. This meansthat the pump system will remain in a standby mode until power isremoved and then, after a brief pause, reinstated. It is during thispause time that technicians can attend to empty supply vessels or anyother matters that might have caused excess load on the system.

It is further desirable that there be some visual indication that thepumping system is in an interrupted or not interrupted state. Suchvisual indication is preferably provided by a red light 222, if thesystem is in an interrupted state, and a green light 224 if it isrunning properly. The circuit 226 for accomplishing this task utilizesthe full wave rectifier 174 described earlier for assuring properrotational direction with slight modifications as shown in FIG. 14. Ifthe PTC 220 is in the non-tripped state, the voltage drop across it willbe too low to illuminate the red LED 222. Full driving voltage will,however, be across the motor terminals so that the green LED 224 isilluminated. If the PTC 220 trips, full voltage will appear across thePTC 220 so that the red LED 222 illuminates. This condition will beaccompanied by loss of voltage across the motor terminals and the greenLED 224 will extinguish.

As a result of the present invention, a simply designed system liquidpumping system is provided, wherein gas bubbles are dispatchedautomatically while replacement of an empty liquid chemical supply tankand commissioning of a new full tank is simply done by switching inputtubing from the empty to the full tank. The system requires no primingand does not require the pump to be turned off when changing liquidsupplies. The pumps of the system are substantially leak-free,rupture-free and less prone to chemical precipitate build-up withresultant mechanical failure.

The system of the present invention is particularly suitable forimplementation as part of a chlorination system, wherein relativelysmall amounts of sodium hypochlorite (NaOCl) solution are injected orfed into a water stream. Such chlorination systems include thoseutilized by municipal water providers and swimming pool facilities.

In these applications, the system is less vulnerable to the corrosiveeffects that chlorine vapors have on the various metal components of thesystem. The system further includes safe-guards to ensure chlorinepumping in only one direction and to ensure that the system componentswill not be damaged in the event of a loss of supply liquid.

Although preferred embodiments of the present invention have beendescribed herein with reference to the accompanying drawings, it is tobe understood that the invention is not limited to those preciseembodiments and that various other changes and modifications may beaffected herein by one skilled in the art without departing from thescope or spirit of the invention, and that it is intended to claim allsuch changes and modifications that fall within the scope of theinvention.

What is claimed is:
 1. A chlorination system for feeding a chlorinesolution into a supply of water, the system comprising: a source ofchlorine solution; a case mountable adjacent said source of chlorinesolution, said case defining a back interior surface; a generally planarzinc coated back plate attached to said back interior surface of saidcase, said back plate substantially covering said back interior surfaceof said case; a zinc motor mounting plate mounted to said back plate; amotor mounted to said mounting plate; and a first pump mounted to saidback plate and driven by said motor for pumping the chorine solutionfrom said source into a supply of water.
 2. A chlorination system asdefined in claim 1, further comprising: a second pump mounted to saidback plate and driven by said motor; and a separator in fluidcommunication with said source of chlorine solution and said first andsecond pumps for separating chlorine solution received from said sourceinto a gaseous component and a liquid component, said separator furtherdiverting said gaseous component to said second pump and said liquidcomponent to said first pump, wherein said second pump pumps saidgaseous component back to said chlorine solution source and said firstpump pumps said liquid component into the supply of water.
 3. Achlorination system as defined in claim 1, wherein said first pump ismounted to said back plate with stainless steel fasteners.
 4. Achlorination system as defined in claim 1, wherein said motor comprises:a rotatable motor shaft; in contact with said zinc coated mounting platevia a steel bearing; and a spherical steel coupling coupled between saidmotor shaft and said first pump.
 5. A chlorination system as defined inclaim 1, wherein said back plate is attached to said interior surface ofsaid case with stainless steel screws.
 6. A chlorination system asdefined in claim 1, wherein said first pump includes a pump mountingbase mounted to said back plate via stainless steel screws.
 7. Achlorination system as defined in claim 1, further comprising anelectrical terminal for providing electrical power to said motor from anelectrical source, said electrical terminal being mounted to said backplate via stainless steel screws.
 8. A chlorination system as defined inclaim 7, wherein said electrical terminal comprises terminal screws forconnecting electrical wiring from the electrical source, and whereinzinc washers are provided under the terminal screws.
 9. A chlorinationsystem as defined in claim 2, wherein all metal components of saidmotor, said first pump, said second pump and said separator aremechanically and electrically connected to at least one of said backplate or said mounting plate.
 10. A chlorination system as defined inclaim 4, wherein said motor further comprises a motor housing and zincalloy housing end caps provided at opposite ends of said housing, saidmotor shaft being in contact with at least one of said zinc alloyhousing end caps.
 11. A chlorination system, as defined in claim 4,wherein said spherical steel coupling is rotatably received within asteel bearing race, said steel bearing race being retained within analuminum pump coupling housing, said aluminum pump coupling housingbeing fixed on an end of said motor shaft, thereby providing anelectrical path between said spherical steel coupling and said zincmotor mounting plate, whereby zinc components are sacrificed to protectsaid spherical steel coupling from corrosion.